1. Field of the Invention
This invention relates to a vibration isolating device for damping vibrations from vibration source, and more particularly to an improvement of a partition member provided with a restricted passage, which divides a vibration isolating body into two liquid chambers and defines a flow resistance to the liquid to thereby produce a damping action, in the vibration isolating device.
2. Description of the Prior Art
The vibration isolating device such as a rubber vibration isolator is used, for instance, as an engine mount for automobile vehicles, whereby vibrations from an internal-combustion engine are absorbed so as not to be transmitted to a vehicle chassis.
As the vibration isolating device of this type, there has been proposed a vibration isolating device comprising two vibration-damping liquid chambers separated by a partition member provided with a restricted passage, in which vibrations from vibration source are absorbed by a flow resistance subjected to the liquid when the vibration is transmitted to the one chamber to thereby flow the liquid from the one chamber to the other through the restricted passage or the orifice.
In this connection, a large damping effect can be produced by prolonging the longitudinal size of the orifice. For this end, there have hitherto been adopted a method wherein a component provided at its outer surface with a spiral groove is inserted in an inner sleeve to form a spiral-type long orifice as in the U.S. Pat. No. 4,277,056, a method of using a pair of disc-like cast articles provided with a communication groove (Japanese Patent laid open No. 57-9,340), and the like.
In these methods, however, the cutting and casting operations requiring a long working time are used, so that the production is complicated and the cost thereof increases.